1. Field of the Invention
The invention relates to a process for the production of 1-n-dodecylazacycloheptan-2-one and more particularly relates to an improved process of systhesis of 1-n-dodecylaza cycloheptan-2-one using tetrabutylammonium bromide or triethylbenzylammonium chloride as phase transfer catalyst under anhydrous solid-liquid phase conditions.
2. Background of the Prior Art
1-n-dodecylazacyoloheptan-2-one is in the form of colourless, odorless oily liquid having the following formula: ##STR1## It is well known as a penetration enhancer. When incorporated into pharmaceutical preparations or into nutriment cosmetics, it can greatly enhance the penetration of active components through the skin, thus diminishing the amounts of active ingredients used in pharmaceutical preparation or nutriments used in cosmetics.
This compound is suitable for agricultural use with insecticides, fungicides and herbicides. It can also be used as a dying enhancer for fiber or synthetic fiber to enhance dye penetration of fibers and to allow the dying process to take place at lower temperature in a shortened period. Therefore, this compound has wide and important industrial applications.
The conventional process of preparing 1-alkyl substituted azacycloalkan-2-ones is based on the reaction of alkali salts of azacycloalkan-2-ones with alkylating agents; See for example, L. Ruzicka, Helv. Chim. Acta 4, 472(1921); C. S. Marvel et al., J.Org.Chem.22,1065 (1957); U.S. Pat. Nos. 3,989,815, 3,989,816 and 4,122,170. In the prior art, the alkali salts of azacycloalkan-2-ones are prepared by treating azacycloalkan-2-one with alkali metals or alkali metal hydrides in the presence of an inert solvent under nitrogen atmosphere. This prior art method, however, is uneconomical because of the costly alkali metals, alkali metal hydrides, and the large amount of solvent required.
EP No. 0095096 discloses an improved method of synthesis of 1-substituted azacycloalkan-2-ones wherein the N-alkylation is carried out in the presence of phase transfer catalysts. The reaction is run from about 20.degree. C. to about 50.degree. C. and over a period of from 50 hours to about 200 hours. The solvent used in the reaction includes aromatic hydrocarbons such as benzene, toluene, and aliphatic hydrocarbons.
This method, however, also possesses many disadvantages. Firstly, a liquid-liquid phase transfer catalysis, having an aqueous phase and an organic phase, is used in the process. Due to the presence of water, coextraction of some water of hydration often occurs during the reaction, resulting in a low yield of the end product and the reaction being completed over a long period of time. Secondly, the solvents toluene, which is poisonous and of a high boiling point, and ether, which are inflammable and explosive, is used in the process, resulting in the production of the compound being not only costly, but also harmful to workers. Therefore, the process is not suitable for large-scale production in industry.